Boiling water nuclear reactors typically include a reactor core located within a reactor pressure vessel (RPV). A known RPV includes a substantially cylindrical shell. The shell, for example, can be about twenty feet in diameter and about seven inches thick.
The cylindrical shell is closed at its top end by a removable top head. The top head is removable so that components, such as fuel bundles, located in the RPV can be accessed. The RPV cylindrical shell is closed at its bottom end by a dome shaped bottom head assembly welded to the shell.
The RPV typically is supported by a conical RPV support skirt and reactor pedestal, and extends into an upper containment. Particularly, one end of the support skirt is welded to the RPV and the other end of the support skirt is secured directly to the reactor pedestal.
Known support skirts typically restrict horizontal, vertical, azimuthal and radial movement of the RPV. Particularly, such skirts are directly coupled between the RPV and the reactor pedestal, and are configured to substantially prevent any movement of the RPV during operation. Restraining vertical, horizontal and azimuthal RPV movement is, of course, desirable to maintain the stability of both the RPV and the RPV internals.
During RPV operation, heat generated within the RPV causes the RPV to expand. Heat and other forces typically cause the RPV to expand radially and vertically. However, the reactor pedestal remains cool, at least with respect to the RPV, and thus typically does not expand. Accordingly, the reactor pedestal does not accommodate radial RPV expansion, i.e., resists radial movement of the support skirt, and may cause high stresses adjacent the support skirt. Over the life of the RPV, these high stresses may reduce the fatigue life of the RPV, which is undesirable.
Accordingly, it would be desirable to provide a support assembly which substantially restrains azimuthal, lateral, and vertical RPV movement while allowing radial RPV expansion. It also would be desirable to provide such an assembly which is easy to install and maintain.